feat: show agent goal in operation messages

- Include agent goal preview in pending/started messages so users can
  distinguish between parallel agent creations
- Remove duplicate "You can close this tab" text from frontend widget
  since it's now in the backend message

autogpt_platform/frontend/src/components/contextual/Chat/components/PendingOperationWidget/PendingOperationWidget.tsx

@@ -77,7 +77,7 @@ export function PendingOperationWidget({
 
             {isPending && (
               <Text variant="small" className="italic text-slate-500">
-                You can close this tab. Check your library in a few minutes.
+                Check your library in a few minutes.
               </Text>
             )}